Journal of the American Ceramic Society, Vol.102, No.5, 2472-2481, 2019
Multi-phase glass-ceramics containing CaF2: Er3+ and ZnAl2O4:Cr3+ nanocrystals for optical temperature sensing
Oxyfluoride transparent glass-ceramics (GC) containing CaF2 and ZnAl2O4 nanocrystals have been fabricated with melt-quenching method. By carrying out the heat treatment of the precursor glass (PG), Er3+ and Cr3+ were selectively partitioned into CaF2 and ZnAl2O4 nanocrystals, respectively. The obtained multi-phase GC exhibited strong upconversion (UC) fluorescence of Er3+ as well as intense down-conversion (DC) fluorescence of Cr3+. Under 980 nm excitation, the green UC fluorescence of Er3+ due to H-2(11/2),S-4(3/2) -> I-4(15/2) transition and the red DC fluorescence lifetime of Cr3+ due to E-2, T-4(2) -> (4)A(2) transition were found to be highly dependent on the temperature and makes them possibly suitable for Optical Thermometry. With least-square fitting methods, the FIR of Er3+ from thermally coupled energy states (H-2(11/2) and S-4(3/2)) produced maximum temperature sensing sensitivity values of 0.33% K-1 at 437 K and 0.36% K-1 at 267 K, respectively. Similarly, fluorescence lifetime of Cr3+ attributed to the parity forbidden (E-2 -> (4)A(2)) and spin allowed (T-4(2) -> (4)A(2)) produced the maximum temperature sensor sensitivity value equal to 0.67% K-1 at 535 K.